Taking detailed notes is terribly inefficient. It can still be the best option if there will be no chance to look up the details later, and if you are a rare person who can write rapidly while thinking about something else. If the slides or paper or lecture notes will be available later, then what's the point of detailed notes? Write down key ideas, or when something is surprising.
I'd appreciate it if everyone were to make lecture notes or at least slides available on the web after a talk. It does take a little more effort, and it makes it more obvious when you give the same talk at conference after conference. However, if you really want to communicate, you can tell more to people who aren't writing at the same time.